(1) Field of the Invention
The present invention relates to a photographic light-sensitive film having an improved layer containing gelatin and an ionic copolymer.
(2) Description of the Prior Art
It is known to increase the covering power of gelatino-silver halide emulsions by the substitution of various polymeric materials for part of the gelatin binder. Jennings, U.S. Pat. No. 3,063,838 discloses that covering power of gelatino-silver halide emulsions can be increased by the addition of dextran. The use of dextran, however, tends to produce optical haze. C. G. Dostes et al, Fr. Pat. No. 1,501,821 discloses gelatin subjected to enzyme treatment or enzyme treatment followed by reaction with an acid anhydride can be substituted for up to 50 percent by weight of the total gelatin of a gelatino-silver halide layer to increase covering power. However, the increase in covering power is not comparable to that of emulsions containing dextran. It is also known to add modified hydrolyzed gelatin (MHG) (U.S. Pat. No. 3,778,278, B. Rakoczy) to gelatino-silver halide emulsions to increase covering power to a level at least equal to that of an emulsion containing dextran, without haze. However, the addition of MHG tends to soften the binder.
Using the ionic copolymers of the invention, covering power is increased without any deleterious effects on film hardening or sensitometry.